1. Field of the Invention
The invention relates to a process for working up waste such as, e.g., residual waste from domestic garbage, industrial waste, bulky refuse or sewage sludge, in which the waste or the sewage sludge is subjected to pyrolysis under an oxygen-poor atmosphere and the solids are subjected to mechanical treating and screening. The invention also relates to an arrangement for carrying out said process.
2. Description of the Related Art
For working up waste it has already been suggested to subject waste comprised of domestic garbage, industrial waste similar to domestic garbage, bulky refuse and sewage sludge to pyrolysis in a first process step. After such a pyrolysis, which was carried out at temperatures of below 500.degree. C. and, most frequently, at temperatures of approximately 450.degree. C. under oxygen-deficient conditions, in known processes cooling to temperatures of below 150.degree. C. was, for instance, realized by means of a cooling vibration conveyor, whereupon a coarse fraction and a fine fraction were formed in a screening means. In the course of that conversion or carbonization at low temperatures, it could be determined that the coarse fraction primarily contained ferritic metals, nonferrous metals and inert material such as, e.g., glass, ceramics, stones and porcelain, whereas the fine fraction contained almost all of the carbon from the waste charged. The fine fraction having grain sizes of above 1 mm in known processes was comminuted and subjected to high-temperature combustion along with the low temperature carbonization gas. Due to the elevated carbon concentration in the fine fraction, a fuel having a high calorific value was provided. Subsequent high-temperature combustion was used to produce energy and, in particular, to produce electric energy or long-distance energy. This high temperature combustion produced an ash melt or slag which could be granulated to a vitrified slag granulate material in a water bath.
Furthermore, it has already been suggested, following the pyrolysis of residual waste, to carry out an extensive chemical reduction in a first step, whereupon oxidation was conducted in several steps in order to be able to discharge valuable substances and, in particular, metal fractions separately.